14 Nov
2019
14 Nov
'19
1:15 a.m.
BTW, I'm doing my first messing around with the Linux kernel these days;
if anyone knows the guts of the generic filesystem code I could use a bit
of help. Here's something that I came across on the way in <sys/mount.h>:
enum
{
MS_RDONLY = 1, /* Mount read-only. */
#define MS_RDONLY MS_RDONLY
MS_NOSUID = 2, /* Ignore suid and sgid bits. */
#define MS_NOSUID MS_NOSUID
MS_NODEV = 4, /* Disallow access to device special files. */
#define MS_NODEV MS_NODEV
...
};
Can anyone explain the value of this programming style? Is this just an
example of the result of how programming is taught today?
This really is more a C question than a UNIX one. The problem is that
the preprocessor macros are really kind of a kludge. Making things
either enums (or in later C/C++ const int definitions) is a lot cleaner.
The #define is just probably backwards a compatibility kludge (for people
using things like MS_RDONLY or whatever in other macros).